1. Field of the Invention
The present invention relates to an input/output device for information processing apparatus such as a computer and the like and, particularly to a two-dimensional image read/display device which is able to read and display information including two-dimensional images.
2. Description of the Related Art
In general, information processing apparatus is equipped with an image display device for displaying information. Examples of such an image display device are a CRT display device, a liquid crystal display (LCD) device, an EL display device (ELD), a plasma display device (PDP), a light emitting diode (LED) display device. In particular, recently, with the development of a high density packaging technology, there have been developed a portable personal computer including an integrated circuit (IC), onto an LCD display substrate of which an IC for driving a display is mounted, and an information processing device of a pocketbook size and the like.
Now, recently, there have been increased the number of such information processing machines and apparatus as include an image input device in addition to the above-mentioned image display device and, in view of this, there have been proposed image display devices each of which includes an image input device added thereto. For example, there has been proposed an image display device which includes a light input type of light pen added thereto in Published Unexamined Japanese Patent Application No. sho-62-37729. Besides this, there are proposed an image display device which employs a capacity coupled type of light pen, an image display device of a pen touch type using a resistance method, and other similar image display devices.
However, in the above-mentioned conventional light pen method and pen touch method, only the image that is drawn by an operator can be input and the image of an original document in which a desired image is drawn cannot be read. In view of this, there is developed a combination of a display device with an image read device which is able to read a two-dimensional image. For example, actually, there is disclosed in Published Unexamined Japanese Patent Application No. Hei-1-106467 a display device in which display elements and image read elements are formed on the same substrate. However, in this display device, because the display elements and image read elements are formed in the different areas of the same substrate, it is necessary to add an illumination device such as a light source or the like to the device, inevitably resulting in the large-sized device.
Also, the conventional image read device is, for the most part, a one-dimension contact type image sensor and, therefore, in order to read a two-dimensional image, there is required a drive system which is used to drive an original document or image sensor. This results in a large-sized image read device which is not suitable for portable information processing equipment. On the other hand, a one-dimension image sensor may be used and a sub scanning operation may be executed manually, so that a two-dimensional image can be read. In this case, a compact image read device can be realized and thus such compact image read device is suitable for a portable information processing device. However, the sub scanning operation cannot be performed due to camera movement and the like, with the result that an image cannot be read with accuracy.
Further, there have been proposed in Published Unexamined Japanese Patent Application Nos. sho-53-119619 and sho-59-149456 two-dimensional image sensors. However, such a two-dimensional image sensor requires an illumination device which is used to move a light source, resulting in a very large-scaled image sensor.
As an image input device for a facsimile and the like, there is known an elongated contact type image sensor including a large number of light receiving elements which are arranged in a line and adapted to convert information from an original document photoelectrically. This image sensor is a line type of (one dimensional) image sensor in which a large number of light receiving elements are arranged only in a line in a main scanning direction.
The above-mentioned conventional one-dimensional image sensor includes, for example, a TFT drive type of image sensor. The TFT drive type of image sensor, as shown in an equivalent circuit diagram of FIG. 1, includes a light receiving element array 51 comprising a plurality of light receiving elements 51" arranged in a line substantially equal in length to the width of an original document, a charge transfer part 52 comprising of a plurality of thin film transistors Ti,J (i=1-N, j=1-n) respectively corresponding to the light receiving elements 51" one for one, a matrix-shaped multi-layer wiring 53, common signal lines 54 respectively guided from the multi-layer wiring 53, a driving IC 55 for sequentially reading out the potentials of the common signal lines 54, a gate pulse generation circuit 56 for applying a gate pulse VG to the charge transfer part 52, and an output line (COM) 57 for outputting in time series the potentials read by the driving IC 55.
To read a two-dimensional image by use of the above-mentioned one-dimensional image sensor, the same light receiving elements must be used repeatedly and, for this reason, the voltage of the gate pulse VG is applied to the same light receiving elements at a certain cycle to thereby read a signal. Thus, when taking into consideration the rising and falling characteristics of a current with respect to the variations in illumination intensity from the blank portion of an original document to the printed or black portion thereof or from the black portion of the original to the blank portion thereof, the speed of the image sensor to read the original is limited.
In order to solve the above problem, there have been developed the above described two-dimensional image sensors. However, as mentioned above, the two-dimensional image sensor requires an illumination device which is adapted to move a light source and, therefore, the whole image sensor provides a large-scale device which is difficult to manufacture as a commercial product. That is, it has a structure which is not suitable especially for a portable use.
Also, referring to one-dimension image sensor, there has been developed a complete contact type of image sensor with a built-in light source which is shown in FIGS. 2 and 3, aiming at realizing a compact device. The complete contact type of image sensor is constructed, as shown generally in FIG. 2, in such a manner that a light source 1 is disposed below a substrate 21 of the sensor and a roller 2 is disposed in the upper portion of the sensor.
Referring to the concrete structure of the conventional image sensor, as shown in FIG. 3 which is an explanatory view of a section in the sub-scanning direction of a sensor part thereof, a light shield layer 26 is formed on the substrate 21, the light shield layer 26 is partly taken away to thereby provide a lighting window 27 which takes in light from the back surface of the substrate 21, a light receiving element 22 is disposed on the top of the light shield layer 26, and there is provided a protection film 28 in such a manner that it can cover all these components.
Referring to the operation of the above-mentioned conventional image sensor of a complete contact type, the light from the light source 1 is allowed to enter from the back surface of the substrate 21 through a lighting window 27, the light reflecting on an original document 3 is received by the light receiving element 22, and electric charges corresponding to the amounts of the light received are read out (see Published Unexamined Japanese Patent Application No. sho-59-122273).
However, in the above-mentioned conventional image sensor of a complete contact type, as shown in FIG. 4 which is an explanatory view of a section of the sensor portion in the main scanning direction, there is a possibility that the incident light entering from a lighting window in an adjoining area may also be received by the light receiving element 22, thereby worsening the resolution of the image sensor to a great extent.
Also, in a conventional portable image input device which uses the image sensor of a complete contact type shown in FIG. 3, when reading a two-dimensional image, scanning is normally executed by hand and an image reading time is synchronized with the speed of the manual scanning. However, it has been conventionally pointed out that such manual scanning is not able to read a figure and the like with accuracy because of movement of the hands.
On the other hand, in information processing machines and apparatus, an image input/output device is widely used and a display, which is one of image output devices, includes various types of devices such as CRT, LCD, ELD and the like. As a modification for these types of displays, there has been developed a composite display which comprises a display and an input device added thereto. For example, there have been disclosed a light pen of a light input type or of a capacity coupled type (see Published Unexamined Japanese Patent Application No. sho-62-37729), a touch pen using resistance. Here, in order to confirm the two-dimensional image that is read, it is convenient if a two-dimensional image reading device and a display device are integrated into one device. However, conventionally, there has not been available an integrated device which can answer to the need that the image can be displayed on the actual spot.